Question

Which of the following is a top down approach for the synthesis of nanomaterials?

• A. Chemical vapour deposition
• B. Physical vapour deposition
• C. Ball Milling
• D. Sol gel process

Hint:

Top-down = breaking bulk material (e.g., ball milling); Bottom-up = building nanoparticles (e.g., sol-gel, CVD).

Answer 1

The Correct Option is C

Step 1: Approaches in nanomaterial synthesis.
- Top-down: Start with bulk material and break it into smaller nanosized particles.
- Bottom-up: Build up nanostructures atom by atom or molecule by molecule.
Step 2: Classification of options.
- Chemical vapour deposition: bottom-up.
- Physical vapour deposition: bottom-up.
- Sol-gel process: bottom-up.
- Ball milling: mechanical grinding of bulk → nanosized particles (top-down).
Final Answer: \[ \boxed{\text{Ball Milling}} \]